That estimate includes both direct and indirect jobs, and it includes not just a subset of the spending that has to be reported on through recipients, but the full set of Recovery Act activities that are out there in the field creating economic activity so far.
The numbers are hard to estimate, but between direct hiring, hiring through labor contractors, and off-the-books work beside parents or for cash, perhaps 400, 000 children, some as young as 6, weed and harvest for commercial farms.